This invention relates to an ultrasonic power meter, and more particularly, to a meter which incorporates a liquid crystal cell as an acoustic detector.
Ultrasonic inspection devices are being used in increasing numbers in industrial and medical applications. In such devices a beam of ultrasonic or acoustic energy is directed at the body to be examined and the ultrasonic energy passing through or reflected from said body is detected and visually displayed to show internal features of the body. In industrial applications such inspection techniques are usually used to detect failure-initiating internal flaws. In medical applications ultrasonics are used diagnostically to inspect internal organs, examine a fetus, and the like.
In all applications it is desirable to maintain the incident energy at the lowest effective level. It may also be desirable to measure and quantify the incident energy. In medical applications it is particularly desirable to quantify and keep the incident energy at the lowest effective level so as to avoid injuring a patient. Depending upon the application, it may also be desirable to measure or quantify the acoustic energy reflected from and/or transmitted through the body.
Meters for measuring acoustic energy are described and disclosed in U.S. Pat. No. 3,137,837, E. S. Wreford and in Physical Principles of Ultrasonic Diagnosis by P. N. T. Wells, Academic Press, London, England. Those references disclose the use of heat, radiation and suspended aluminum flakes to detect the ultrasonic energy incident on the measuring device. However, such devices are not in widespread commercial use. It also appears that the meter disclosed in U.S. Pat. No. 3,137,837 may have drawbacks due to the aluminum flakes used therein. For example, gravity causes the flakes to settle to the bottom of the cell and thus cause uneven and unreliable results. Furthermore, the flakes may chemically react with the suspension and chemically degrade the cell, and it is known that the response time for the aluminum flakes is poor.
It is an object of this invention to provide a device in which the detector will uniformly respond to incident acoustic energy and to an applied electric field.
It is another object to provide a meter in which the detecting medium is stable, does not chemically degrade and has an acceptable response time.
It is still another object of this invention to provide an easily used and commercially acceptable meter which can be used in industrial and medical applications.
These and other objects of the invention will become apparent from the following description and appended claims.